1. Field of the Invention
This invention relates to a method of manufacturing a titanium alloy article, and particularly to a method of manufacturing a titanium alloy article by means of a powder metallurgy sintering method.
2. Description of the Prior Art
Titanium is a material of high strength, lightweight, and highly anticorrosive. In the prior art, a titanium alloy article can be manufactured by methods such as casting, powder metallurgy (P/M) sintering, and sheet pressing. The casting method results in an alloy article of high strength but with an unstable quality, a bad throughput, and a high cost. The conventional powder metallurgy sintering method has disadvantages such as a low density, an insufficient tensile strength and extensibility. The sheet pressing method has disadvantages such as a high mold-wearing rate, a poor changeability in shape, and a poor accuracy, due to the high hardness of the titanium alloy. By means of the sheet pressing method, right-angle portions of an article are not as good as expected.
As far as the conventional powder metallurgy sintering method is concerned, in addition to a conventional powder-compression-molding method, a powder-inject-molding method has been proposed to overcome the disadvantage of insufficient strength. The conventional powder-compression-molding method needs a large amount of lubricant, serving as a disengaging agent, to easily release an unbaked article from a die and to prevent the die from becoming jammed. However, since the lubricant cannot be completely expelled from the titanium alloy article in the conventional powder metallurgy sintering method, the density of the sintered titanium alloy article is relatively low. The powder-inject-molding method uses titanium powder of smaller diameter as well as a large amount of lubricant much more than in the powder-compression-molding method. To expel the lubricant, a chemical method incorporated with particular equipment has ever been proposed. However, such a chemical method is costly and requires a long processing time. In addition, the titanium alloy article produced by such a sintering and chemical method can only have a density of no more than 95% of theoretical density and a strength inferior to that of the casting method.
On the other hand, with various superior properties, titanium alloy has been applied to various articles such as the frame for glasses and the hitting face of a golf club. In the case of the hitting face, a titanium hitting face manufactured by the casting and cutting method is very expensive. As for the use of the pressing method to alternatively manufacture the hitting face, it has a problem to obtain a well-defined shape. This is one of the reasons that a stepped edge is necessary for a hitting face and the stepped angle for the stepped edge should be very precise so that the hitting face can be fit into a head of a club. Moreover, in case a hitting face is manufactured by the conventional powder metallurgy sintering method, the hitting face is of insufficient strength. Thus, the conventional sintering method is not appropriate to produce a high-quality hitting face. In view of the above, the existing manufacturing methods cannot produce a titanium alloy article having high stability, a more precise pattern, high strength, and high density at a low cost, especially for a hitting face of a club.